1. Field of the Invention
The present invention relates to magnetic recording/playback heads, and, in particular, to such heads having at least one transducer for recording servo information to subsequently control the transverse position of a plurality of read/write transducers for multi-channel recording and playback of data.
2. Description of the Prior Art
It is very common to provide magnetic recording head assemblies having a plurality of recording/playback transducers positioned transverse to the intended path of a magnetic recording medium for writing data on and reading data from parallel tracks on the medium. It is also well known to include servo information on at least some of the tracks to enable control of the lateral position of the head assembly, thereby dynamically maintaining the respective transducers of the assembly centered on a respective track. The track widths can then be made significantly narrower, and the areal density of recording similarly increased.
A number of techniques for providing the servo information-containing tracks have been previously employed, each technique having certain attributes and certain deficiencies. Thus, for example, it is known to provide dedicated servo tracks on the medium at the time of manufacture. Such a technique, of course, prevents an end user from writing the servo information on an unformatted medium, and may result in unacceptable inaccuracies depending upon the variability of transducer spacings in various drives.
Accordingly, it is desirable to enable an end user to write the servo pattern on the medium while it is in the recorder/drive. An end user may then preformat, i.e., add the servo information to either a blank medium or utilize a medium which was either intentionally or unintentionally erased. Previously-known methods available to the user have included the use of a dedicated drive for servo recording only. Such a method is generally unacceptable due to the cost and inconvenience, particularly to users of small systems where only one drive can be afforded. Other methods require the drive to include a separate auxiliary head, which adds complexity to the drive, is a significant additional cost, and cannot probably be done within typical space envelopes of most drives.
One technique for providing the servo tracks by way of a separate, auxiliary head is disclosed in U.S. Pat. No. 4,979,051 (Eggebeen). The head assembly there depicted is primarily intended for use with multi-layer magnetic recording tape in which the servo information is buried, i.e., recorded on an underlying, high-coercive force layer, while actual user data is recorded directly thereover in an upper layer having a lower coercive force. The head assembly is shown to include two components: a first servo write transducer having a write face which extends the full width of the magnetic recording tape with which it is to be used, and a second servo write transducer which is spaced from the first and has a write face of the same overall width, but which contains a plurality of alternating contact and non-contact portions. A second servo signal is to be applied to the contact portions so as to continuously write that signal over the first servo signal.